The casting process of ductile iron is roughly the same as that of ordinary cast iron, and the casting molding process is different. Strictly speaking, the casting process of ductile iron is more strict. The following describes the entire casting process and description in detail.

Nodular cast iron casting process

✔️Foundry material selection

In the production of ductile castings, ordinary gray cast iron cannot be used as raw material, and qualified ductile iron must be used. For example, No. 18 ductile iron is a commonly used ductile iron. When smelting and batching, the ingredients are combined with the content of the raw material test sheet. agent.

✔️Modeling process introduction

The difference between the molding process of ductile iron and ordinary gray iron castings is that the shrinkage of ductile iron in casting is larger than that of ordinary gray iron castings. Therefore, the size of the riser should be increased during modeling to ensure that the molten iron in the riser can fully supplement the needs. shrinkage. Due to the characteristics of ductile iron, cement sand cannot be used as molding sand for molding. Resin sand or water glass sand should be used for molding, and high temperature refractory materials should be selected for refractory coatings.

✔️Melting and casting process description

Smelting is to strictly control the content of ductile iron. For example, the material of ductile iron is required to be QT450, and the content of the five elements ranges from C: 3.55-3.75% Si: 2.5-2.7% Mn: 0.3-0.45% P: ≤ 0.1% S:≤0.02%. When casting, the principle of high temperature casting and low temperature casting should be adopted. After the start of casting, it is necessary to ensure that each riser can be filled with molten iron, and continue to replenish molten iron to the riser until the molten iron in the riser does not sink and decrease.

In order to ensure the quality of the ductile castings, the press box iron cannot be withdrawn too early, and if conditions permit, it should not be withdrawn as much as possible. It is necessary to wait for the ductile castings to reach a certain temperature before unpacking them. Remember to unpack them at high temperatures too early.

What is the carbon content of ductile castings:

Carbon is the basic element of ductile castings, and high carbon can promote the graphitization of castings. Since the graphite is spherical, the graphite can absorb energy to the machine and improve the physical properties of the machine. The carbon content of ductile iron is generally higher and belongs to iron-carbon alloys. The carbon content of industrial cast iron is generally 2% to 3.9%. The carbon equivalent is between 4.1 and 4.7%.

The main components of ductile iron castings: The chemical composition of ductile iron mainly includes sulfur, phosphorus, silicon, carbon, manganese, and five common elements.

The effect of carbon content on the properties of ductile iron:

The carbon content in ductile castings will affect the amount of graphite precipitation during solidification, that is, the average size or number of graphite balls. Usually, the carbon content of ductile castings is generally between 2 and 3.9%, but it is understood that reducing the carbon content is important for The influence of the mechanical properties of the ductile iron is very important. It should be based on the structure, size, wall thickness of the ductile iron casting, the error of the wall thickness of two adjacent planes, and so on. The carbon content in the ductile iron is reduced from about 4% to 2.5%. The tensile strength and elastic limit can be slightly increased (about 23~31N/mm~2), the elongation is increased by about 5%, and the maximum impact value Great improvement.

Conclusion

The above steps are the basic flow of the ductile iron casting process. When producing ductile iron castings, the above steps must be strictly followed. For ductile iron castings of special size or structure, the specific casting process flow should be refined to ensure the quality of the castings. and quality.

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